The discovery of the laws of thermodynamics in the 19th century rose many fundamental questions. Among them, the Maxwell’s demon thought experiment appears to be one of the most interesting because of its apparent violation of the second principle. This paradox has only been solved in the late 60s by considering the thermodynamical cost of information, and one had to wait until 2010 to see its first experimental realization. But one question remains : what if the constituents considered are quantum ? We realized a quantum-mechanical version of the Maxwell’s demon based on a circuit quantum electrodynamics architecture. We characterized the flows of energy and entropy in every constituent at each step of the experiment. Moreover, we have achieved a direct measurement of the work extracted by the demon by performing the first measurement of stimulated emission in the microwave domain.